Mountain Province Diamonds saw the average price of rough at its September sale fall to the lowest level yet, as the tender included an unusually large proportion of small stones and fewer high-end goods.

The company sold 463,000 carats of rough diamonds at an average price of $59 per carat, bringing total proceeds to $27.1 million, it said in a statement Monday.

  The sale of goods from the company’s Gahcho Kué mine in Canada featured a relatively high volume of diamonds, as a procedural change by the Government of the Northwest Territories enabled the miner to bring smaller rough to the market sooner than it could in the past. However, this had a negative effect on the average selling price.

  The sale also included fewer fancy and special diamonds than previous tenders did, as De Beers, Mountain Province’s partner in the mine, won a bid for these goods. While the two companies share the standard, or “run-of-mine,” production among themselves according to their stakes in the project, they compete against each other for the fancy and special stones.

   Production at Gahcho Kué started in September 2016, with Mountain Province’s first sale taking place in January. Sales at the first three tenders, which took place in the first quarter, averaged $72 per carat. This rose to $86 per carat at the May sale and to $95 per carat in June, before slipping to $72 per carat the following month. Mountain Province owns 49% of the mine, with De Beers holding 51%.